It's interesting that whenever the topic of the political compass comes up (here and also at DWT and DWM), most of us come out strongly on the libertarian scale (small l). We have our differences on the economic scale, but we all tend to agree that social liberties are good.

... and whilst I think there's agreement that "social liberties are good", some people appear more willing to trade them off than others.

Whilst there's small pockets of "activism" which relate to the fulfillment of liberties (e.g. campaigns to release Julian Assange and other political prisoners), most "activism" in the West seems to be focused on demanding greater levels of state interference and involvement in our daily affairs.

For example, environmental activists often pursue tighter regulations and legislation, bans on plastic bags, and pushes for global governance, targets and quotas.

Social activists focused on "economic" issues often pursue tighter legislation regarding minimum wages, living wages, unemployment benefits, more spending on public schools and public hospitals, the rights of renters, job creation through increased spending... and again, more centrally administered targets and quotas.

If we take the craving for increased authoritarianism as reflective of the "authoritarian" half of the political compass... is there scope for activism on the "libertarian half" of the political compass, whether left or right, and what exactly does it look like?

"He goes to hell, the one who asserts what didn’t take place" (Ud 4.8)
"Let us neither be perpetrators nor victims!" (DN26)
"Transition to greatness" (Donald J. Trump)

... is there scope for activism on the "libertarian half" of the political compass, whether left or right, and what exactly does it look like?

Good question, and I have two answers.
(1) On a personal level, activism consists or doing what one feels to be right, as far as possible, regardless of whether that is in accordance with "authority" (aka laws, social pressures, religion ... ) or not, i.e. in rejecting, in principle, and often in practice, the authority of "authority," asserting one's right to self-determination. I got my black belt in this ten years ago so if you need any more information...
(2) On a social level, it often looks exactly like the "authoritarian" activism you describe, i.e. joining or forming a group to pressure government or the local council or whatever to do such-and-such, ban such-and-such, etc. If a sweeping change is needed, what else could it possibly look like?
But if the goal is limited and local, forming a group to, e.g., revegetate a local park is fine, founding a migrant drop-in centre is fine. The group will look pretty similar but shouldn't raise your hackles because it doesn't try to impose a rule on everyone ... hang on, "There will be native trees here," or "We will all be nice to migrants here," are kinda rules imposed on our community, too.
Okay ... next try.

In short my position is that authoritarian activism against what is deeply destructive is warranted whereas libertarian activism in favor of what is destructive is unwarranted. On the flipside, authoritarian activism against what is not significantly destructive is unwarranted whereas libertarian activism in favor of what is not significantly destructive is warranted. Of course, it then demands to define "destructive". I think it would mean significantly unwholesome (akusala).

First we should recognize that Capitalism is deeply authoritarian by nature, because employers get to tell their employees what rules they have to follow, how they have to dress etc. and employees often have little to no recourse, especially when there is high unemployment.

Second, I think those blanket characterizations are just too simple to grasp the complexity of reality. Take the case of net neutrality. Are those who are protesting in favor of net neutrality protecting the freedom of individuals or trying to regulate ISPs in an authoritarian way? I would say it's both.

There will also be situations where the state will interfere in transactions between people to ban unethical practices and protect those without money nor power, in which case the interference is authoritarian from the standpoint of the wrongdoer but is protecting the freedom of the powerless.

Now to answer Paul's question, it seems to me that anti-war activism could be included in that scope

On a social level, it often looks exactly like the "authoritarian" activism you describe, i.e. joining or forming a group to pressure government or the local council or whatever to do such-and-such, ban such-and-such, etc.